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Advantages and Disadvantages of Multicellular Organisms

• Advantages:

  • Increased size and complexity, allowing specialization of cells and organs (e.g., muscle, nerve, stomach)

• Disadvantages:

  • More complex interactions and processes required to ensure proper functioning of all parts

Coordination in Complex Organisms

• Mechanisms for Coordinating Internal Activities:

  • Communication between cells (e.g., nervous, endocrine, immune systems)

  • Nutrient supply through digestive system

  • Regulation of environmental exchanges (respiratory system, temperature control)

  • Transport within the body (circulatory system)

  • Reproductive processes for continuation of species

Optimal Conditions for Cell Function

• Biochemical reactions (DNA replication, proteinsynthesis, catabolism) needed for a cell to stay aliveand function well depend on physical and chemicalconditions.

• Key Factors Influencing Biochemical Reactions:

  • pH levels

  • Ionic concentrations (Na, Cl)

  • Respiratory gases (CO2/O2)

  • Temperature

• Cells must maintain conditions within a narrow range for optimal functioning.

Mechanisms of Maintaining Organismal Function

• Living organisms require effective strategies to keep tissues and organs functioning amidst challenging environmental conditions.

• Examples of Organism Responses:

  • Some organisms, like small or simple creatures, directly interact with their environment (e.g., Hydra).

  • Larger organisms (e.g., lobsters) may have more complex adaptations to maintain internal functioning.

Example: Lobster Stomach Functionality

• External temperature impacts lobster muscle contractions affecting digestion.

• Hypothesis: Dopamine may be released in response to increased temperature, enhancing muscle contraction and digestion processes.

Homeostasis in Mammals and Birds

• Mammals and birds regulate their internal environment despite external changes.

• Homeostasis Significance:

  • Ability to maintain consistent internal conditions promotes survival and effectiveness in various environments.

Claude Bernard's Contribution to Homeostasis

• Claude Bernard posited that living organisms maintain an 'interior environment' through homeostatic mechanisms.

• Animals should be viewed as having two separate environments : External and Internal

• Maintaining homeostasis is ubiquitous in the way many organisms work.

  • Autonomic nervous system (body temp, heart rate,blood flow)

  • Endocrine system (blood glucose, ion concentrations)

Homeostatic Regulation Overview

• Key Components:

  • Effector: Mechanism modifying the internal environment

  • Receptor: Mechanism obtaining information about current state

  • Sensor: Compares measurable properties against standards

• Homeostatic regulation often depends on negative feedback systems.

• Types of information:

  • Set point – desired value (car example = speed limit)

  • Feedback – linkage from information coming from receptor that feeds into (alters) the parameter being controlled (car example = that foot pushes more on accelerator when car is going too slowly, pushes less when car is going too fast).

Homeostatic Feedback Mechanisms

• Negative Feedback Process:

  • Stimulus < sensor < effector < response

  • Homeostatic regulation typically depends on negative feedback

  • Thermostat example: Cold environment triggers heater response, stabilizing temperature at set levels (set point).

Comparative Aspects of Ectotherms and Endotherms

• Ectotherms: Environmental temperature influences metabolic rate directly.

• Endotherms: Use internal regulatory mechanisms to maintain stable body temperature regardless of external conditions.

Case Study: Human Physiology and Evolution

• Human Adaptations for Endurance Running:

  • Omnivorous diet from early origins; readiness to sweat and regulate body temperature for prolonged physical exertion.

• Environmental Influence: Our evolution in hot climates necessitated adaptations for dissipating body heat effectively during long-distance running.